The present invention relates to an apparatus and method for storing and freezing a liquid. More particularly, the present invention relates to an apparatus and method for collecting, storing, freezing and removing a frozen liquid from a plastic container, wherein the liquid is generally blood plasma.
Blood plasma is usually obtained through volunteer donation. In general, the blood is collected from the donor, processed into its component parts, including plasma, and frozen or stored for future infusion or further fractionation.
To this end, blood may be collected from the donor into an interconnected multiple-bag collection system, such as that marketed by the Fenwal Division of Baxter Healthcare, Inc., of Deerfield, Ill., U.S.A., under product code number 4R1402. In such a system, whole blood from the donor is first collected into a donor bag. The donor bag is then centrifuged to separate the whole blood into two layers: a lower layer of red cells and an upper layer of plasma. The plasma contains platelets, which are instrumental in the clotting process. This plasma is commonly referred to as platelet-rich plasma. The platelet-rich plasma is expressed, usually by manually squeezing the donor bag, into a second bag of the multiple-bag blood collection system.
If there are three bags in the blood collection system, as there are in the above-identified Baxter Healthcare product, the third bag may contain a red blood cell preservative to extend the shelf-life of the red blood cells. The red blood cell preservation solution is transferred to the donor bag and mixed with the packed red blood cells. The tube between the donor bag and the rest of the blood collection system is then sealed and severed.
To further separate the platelet rich plasma into platelets and plasma, the bag containing the platelet rich plasma is again centrifuged. This forms a lower layer of platelets and an upper layer of platelet-poor plasma. The platelet-poor plasma is then expressed into the third bag of the blood collection system and the tube connecting these two bags is sealed and severed.
Following collection and fractionation, some blood components are usually frozen for increased storage life and for ease of transportation to another location. The bags containing the platelet-poor plasma, for example, are typically placed into blast freezers designed for quickly freezing liquids. The frozen plasma is then stored in a storage freezer.
The frozen plasma can be thawed and used for plasma infusion or processed by further fractionation into its component parts, such as serum albumen, antihemophilic factor, fibrinogen, gamma globulin and the like. As a first step in plasma fractionation, the frozen plasma must be removed from the bag. As a result of the soft and pliable nature of vinyl at room temperature, the shape of the vinyl collection bags and the freezing process itself, the plasma tends to freeze in a large bulbous lump in the bottom of the bag. This makes simple removal of the frozen plasma slug very difficult and time consuming. In one removal technique, the blood collection bags are immersed in liquid nitrogen to make the plasma and the bag colder, and thus more brittle. The collection bags are then manually beaten onto a table to fracture the bags. The large chunks of frozen plasma are manually selected from among the broken pieces of vinyl bag material. However, any plasma stuck to a blood collection bag or trapped in a corner, fold, or wrinkle of the bag is swept from the table with the waste. As a result, a significant quantity of the collected plasma also may be wasted in this procedure.
One form of apparatus and method to improve recovery of frozen plasma is described in U.S. Pat. No. 4,253,458. This patent discloses a bag for collection of plasma which is made of a polyolefin material, which material is significantly stiffer than vinyl and generally maintains its as-molded shape. The shape of the polyolefin bag is configured wherein the sides taper substantially from the top towards the bottom, so that the frozen slug of plasma may be more completely expelled from the bag. Although the polyolefin bag improves the efficiency of plasma removal, because it is more rigid than vinyl, it does not provide a lay-flat configuration when empty. Accordingly, fewer containers can be packaged in a given sized shipping container. Moreover, polyolefin containers are considerably more expensive than vinyl, due to material costs and to the blow molding process used to make such containers.
U.S. Pat. No. 4,340,152 discloses a method and apparatus for removing frozen blood automatically from containers such as the container disclosed in U.S. Pat. No. 4,253,458, discussed above. That patent does not, however, address the increased cost of polyolefin containers or the higher shipping cost associated with such containers.
Accordingly, it is a general object of this invention to provide an improved apparatus and method useful for the collection of blood and blood components.
It is a more particular object of this invention to provide an apparatus and method useful in the collection of blood and blood components in vinyl bags.
These and other objects of the present invention are set forth in the following detailed description of the illustrated embodiment of the present invention.